One of the most important requirements in the case of herbicide compositions is the selectivity, that is, the composition has to kill effectively the weeds when used for cultivated plants, while it should exert at most a minimum effect on the development of the cultivated plants. A number of herbicides are known which, in addition to the control of weeds, possess substantial damaging effect on the cultivated plants. Such herbicide are thiocarbamate and chloroacetanilide derivatives.
Thiocarbamate derivatives and herbicide compositions containing these compounds are disclosed in the U.S. Pat. Nos. 2,913,327 and 3,175,897. Of these, S-ethyl-N,N-di-(n-propyl)thiocarbamate (EPTC) and S-ethyl-N,N-diisobutylthiocarbamate (butylate) are widely used in agricultural practice. Chloroacetanilide derivatives are described for instance in the U.S. Pat. Nos. 3,442,945 and 3,547,620. Outstanding representatives of proved value in this group are, for example, 2-methyl-6-ethyl-N-(ethoxymethyl)chloroacetanilide (acetochlor), 2-methyl-6-ethyl-N-(1-methyl-2-methoxyethyl)chloroacetanilide (metolachlor) and 2,6-diethyl-N-(methoxymethyl)chloroacetanilide (alachlor).
Compositions comprising the aforementioned thiocarbamate and chloroacetanilide type active agents possess an excellent herbicidal activity, but also exert a harmful effect on cultivated plants, for example, on maize and other cereals.
In order to reduce or prevent the effect damaging the cultivated plants and to enhance the selectivity, a compound antagonizing this harmful effect, the so-called antidote is mixed with the herbicidal agent or composition, or the herbicide composition is used together with a composition containing an antidote for obtaining the same herbicidal activity without any damage to the cultivated plants.
Antidotes that can be used against the effect damaging cultivated plants and particularly the maize of herbicidal compositions containing thiocarbamates are disclosed for instance in the Belgian patent specification Nos. 782,120 and 806,038; in the U.S. Pat. Nos. 3,893,838 and 3,931,313; in the British patent specification Nos. 1,420,685 and 1,512,540; as well as in the Hungarian patent specification Nos. 176,784, 165,736 and 168,977.
Of these antidotes, N,N-diallyldichloroacetamide, described in the Hungarian patent specification No. 165,736, is generally used in agricultural practice. In addition to this most widely used antidote, the antiphytotoxic (that is phytotoxicity reducing) features of various dichloroacetamide derivatives have been studied in detail.
In one of these papers [Res. Discl. 143, 8 (1976)] the property of reducing the harmful effect of thiocarbamates of a group of heterocyclic compounds containing nitrogen were investigated and it was stated that no damaging effect was observed when for example a combination of N-dichloroacetylhexamethyleneimine with S-trichloroally N,N-diisopropylthiocarbamate (triallate) was used in a 16:1 to 1:4 ratio.
Similarly, the action of dichloroacetamide derivatives has been disclosed in two other papers [J. Agric. Food. Chem. 26, 1,137-40 (1978); and ibid 27, 3, 543-7 (1979)] reporting on the synthesis of dichloroacetamide derivatives and trying to find correlations between the molecular structure of the dichloroacetamide antidotes and thiocarbamates on the basis of analogy.